//============================================================================================================
//
//
//                  Copyright (c) 2023, Qualcomm Innovation Center, Inc. All rights reserved.
//                              SPDX-License-Identifier: BSD-3-Clause
//
//============================================================================================================
#pragma once

/// @file crc32c.hpp
/// Very simple CRC32C checksum calculation.
/// CRC32C polynomial is 0x1EDC6F41/0x82F63B78.
///
/// @note that CRC32C produces different outputs to CRC32 (eg the one in zlib).
///
/// Uses a small (1k) lookup table (in crc32c.cpp) to accelerate (somewhat).
/// Both Intel and Mark Alder have more optimized implementations (with more complexity)
/// and both ARM and Intel have added CRC32C instructions (albeit not in every processor
/// revision).  If speed becomes a concern consider switching over to one of those!

#include <cstdint>
#include <string>
#include <span>

inline constexpr uint32_t crc32c_lookup[256] = {
        0x00000000L, 0xF26B8303L, 0xE13B70F7L, 0x1350F3F4L,
        0xC79A971FL, 0x35F1141CL, 0x26A1E7E8L, 0xD4CA64EBL,
        0x8AD958CFL, 0x78B2DBCCL, 0x6BE22838L, 0x9989AB3BL,
        0x4D43CFD0L, 0xBF284CD3L, 0xAC78BF27L, 0x5E133C24L,
        0x105EC76FL, 0xE235446CL, 0xF165B798L, 0x030E349BL,
        0xD7C45070L, 0x25AFD373L, 0x36FF2087L, 0xC494A384L,
        0x9A879FA0L, 0x68EC1CA3L, 0x7BBCEF57L, 0x89D76C54L,
        0x5D1D08BFL, 0xAF768BBCL, 0xBC267848L, 0x4E4DFB4BL,
        0x20BD8EDEL, 0xD2D60DDDL, 0xC186FE29L, 0x33ED7D2AL,
        0xE72719C1L, 0x154C9AC2L, 0x061C6936L, 0xF477EA35L,
        0xAA64D611L, 0x580F5512L, 0x4B5FA6E6L, 0xB93425E5L,
        0x6DFE410EL, 0x9F95C20DL, 0x8CC531F9L, 0x7EAEB2FAL,
        0x30E349B1L, 0xC288CAB2L, 0xD1D83946L, 0x23B3BA45L,
        0xF779DEAEL, 0x05125DADL, 0x1642AE59L, 0xE4292D5AL,
        0xBA3A117EL, 0x4851927DL, 0x5B016189L, 0xA96AE28AL,
        0x7DA08661L, 0x8FCB0562L, 0x9C9BF696L, 0x6EF07595L,
        0x417B1DBCL, 0xB3109EBFL, 0xA0406D4BL, 0x522BEE48L,
        0x86E18AA3L, 0x748A09A0L, 0x67DAFA54L, 0x95B17957L,
        0xCBA24573L, 0x39C9C670L, 0x2A993584L, 0xD8F2B687L,
        0x0C38D26CL, 0xFE53516FL, 0xED03A29BL, 0x1F682198L,
        0x5125DAD3L, 0xA34E59D0L, 0xB01EAA24L, 0x42752927L,
        0x96BF4DCCL, 0x64D4CECFL, 0x77843D3BL, 0x85EFBE38L,
        0xDBFC821CL, 0x2997011FL, 0x3AC7F2EBL, 0xC8AC71E8L,
        0x1C661503L, 0xEE0D9600L, 0xFD5D65F4L, 0x0F36E6F7L,
        0x61C69362L, 0x93AD1061L, 0x80FDE395L, 0x72966096L,
        0xA65C047DL, 0x5437877EL, 0x4767748AL, 0xB50CF789L,
        0xEB1FCBADL, 0x197448AEL, 0x0A24BB5AL, 0xF84F3859L,
        0x2C855CB2L, 0xDEEEDFB1L, 0xCDBE2C45L, 0x3FD5AF46L,
        0x7198540DL, 0x83F3D70EL, 0x90A324FAL, 0x62C8A7F9L,
        0xB602C312L, 0x44694011L, 0x5739B3E5L, 0xA55230E6L,
        0xFB410CC2L, 0x092A8FC1L, 0x1A7A7C35L, 0xE811FF36L,
        0x3CDB9BDDL, 0xCEB018DEL, 0xDDE0EB2AL, 0x2F8B6829L,
        0x82F63B78L, 0x709DB87BL, 0x63CD4B8FL, 0x91A6C88CL,
        0x456CAC67L, 0xB7072F64L, 0xA457DC90L, 0x563C5F93L,
        0x082F63B7L, 0xFA44E0B4L, 0xE9141340L, 0x1B7F9043L,
        0xCFB5F4A8L, 0x3DDE77ABL, 0x2E8E845FL, 0xDCE5075CL,
        0x92A8FC17L, 0x60C37F14L, 0x73938CE0L, 0x81F80FE3L,
        0x55326B08L, 0xA759E80BL, 0xB4091BFFL, 0x466298FCL,
        0x1871A4D8L, 0xEA1A27DBL, 0xF94AD42FL, 0x0B21572CL,
        0xDFEB33C7L, 0x2D80B0C4L, 0x3ED04330L, 0xCCBBC033L,
        0xA24BB5A6L, 0x502036A5L, 0x4370C551L, 0xB11B4652L,
        0x65D122B9L, 0x97BAA1BAL, 0x84EA524EL, 0x7681D14DL,
        0x2892ED69L, 0xDAF96E6AL, 0xC9A99D9EL, 0x3BC21E9DL,
        0xEF087A76L, 0x1D63F975L, 0x0E330A81L, 0xFC588982L,
        0xB21572C9L, 0x407EF1CAL, 0x532E023EL, 0xA145813DL,
        0x758FE5D6L, 0x87E466D5L, 0x94B49521L, 0x66DF1622L,
        0x38CC2A06L, 0xCAA7A905L, 0xD9F75AF1L, 0x2B9CD9F2L,
        0xFF56BD19L, 0x0D3D3E1AL, 0x1E6DCDEEL, 0xEC064EEDL,
        0xC38D26C4L, 0x31E6A5C7L, 0x22B65633L, 0xD0DDD530L,
        0x0417B1DBL, 0xF67C32D8L, 0xE52CC12CL, 0x1747422FL,
        0x49547E0BL, 0xBB3FFD08L, 0xA86F0EFCL, 0x5A048DFFL,
        0x8ECEE914L, 0x7CA56A17L, 0x6FF599E3L, 0x9D9E1AE0L,
        0xD3D3E1ABL, 0x21B862A8L, 0x32E8915CL, 0xC083125FL,
        0x144976B4L, 0xE622F5B7L, 0xF5720643L, 0x07198540L,
        0x590AB964L, 0xAB613A67L, 0xB831C993L, 0x4A5A4A90L,
        0x9E902E7BL, 0x6CFBAD78L, 0x7FAB5E8CL, 0x8DC0DD8FL,
        0xE330A81AL, 0x115B2B19L, 0x020BD8EDL, 0xF0605BEEL,
        0x24AA3F05L, 0xD6C1BC06L, 0xC5914FF2L, 0x37FACCF1L,
        0x69E9F0D5L, 0x9B8273D6L, 0x88D28022L, 0x7AB90321L,
        0xAE7367CAL, 0x5C18E4C9L, 0x4F48173DL, 0xBD23943EL,
        0xF36E6F75L, 0x0105EC76L, 0x12551F82L, 0xE03E9C81L,
        0x34F4F86AL, 0xC69F7B69L, 0xD5CF889DL, 0x27A40B9EL,
        0x79B737BAL, 0x8BDCB4B9L, 0x988C474DL, 0x6AE7C44EL,
        0xBE2DA0A5L, 0x4C4623A6L, 0x5F16D052L, 0xAD7D5351L
};

/// @brief Generate a crc (using the 32bit crc32c algorithm).
/// is Constexpr so MAY be optimized out by a good compiler (if data is known at compile time)
/// @param crc 'starting' crc value
/// @param data bytes to iterate over (and generate crc for)
/// @return new crc value
static constexpr uint32_t crc32c(uint32_t crc, const std::span<const uint8_t> data)
{
    for (const auto d : data)
        crc = crc32c_lookup[(crc ^ d) & 0xff] ^ (crc >> 8);
    return crc;
}

/// @brief Generate a crc (using the 32bit crc32c algorithm)
/// @param crc 'starting' crc value
/// @param string to iterate over (and generate crc for)
/// @return new crc value
static constexpr inline uint32_t crc32c(uint32_t crc, std::string_view data)
{
    for (const auto d : data)
        crc = crc32c_lookup[(crc ^ d) & 0xff] ^ (crc >> 8);
    return crc;
}

///////////////////////////////////////////////////////////////////////////////

// FNV hashing code (less collisions than crc32 for small runs of data)
inline constexpr uint32_t FnvHash32(std::string_view s)
{
    uint32_t h = 0x811c9dc5;
    constexpr uint32_t prime = 0x01000193;
    for (char c : s) {
        h ^= static_cast<uint32_t>(c);
        h *= prime;
    }
    return h;
}


///////////////////////////////////////////////////////////////////////////////

// FNV hashing code with lowercase conversion of string (assumes/demands C codepage, ie basic ascii, no utf-8 etc)

inline constexpr uint32_t FnvHashLower32(std::string_view s)
{
    uint32_t h = 0x811c9dc5;
    constexpr uint32_t prime = 0x01000193;
    for (char c : s) {
        h ^= static_cast<uint32_t>((c >= 'A' && c <= 'Z') ? (c + 32) : c);
        h *= prime;
    }
    return h;
}

struct FnvHashLower
{
    inline constexpr FnvHashLower(const std::string_view s) : h{ FnvHashLower32(s) } {}
    const uint32_t h;
    constexpr operator uint32_t() const { return h; }
};
